Eastern Tent Caterpillars Hatching Earlier This Year

Eastern tent caterpillar eggs have begun hatching well ahead of last year's schedule, and the egg hatch is expected to be completed by the first full week of March, University of Kentucky (UK) officials said Feb. 29.

Lee Townsend, PhD, an entomologist at the UK College of Agriculture, said caterpillar populations have been sporadic during the last few years with pockets of increased populations in some areas. He said Central Kentucky is seven to 10 days away from being able to see distinct tents in trees with live larvae.

Controlling Eastern tent caterpillars is vital to area horse farms, as UK research has proven the caterpillars caused outbreaks of mare reproductive loss syndrome (MRLS), which can cause late-term foal losses, early- and late-term fetal losses, and weak foals. During the 2001-02 MRLS outbreak, about 30% of that year’s Thoroughbred foal crop was lost.

The state suffered an economic loss of $336 million in all breeds of horses.

Townsend said horse farms should check wild cherry and related trees for Eastern tent caterpillar activity to determine whether management is necessary. If control measures are needed to reduce numbers, steps should be taken before the caterpillars leave their trees.

“The small caterpillars will stay near the egg mass for a short time before moving to feed on expanding leaves,” Townsend said.

Eastern tent caterpillars grow and develop as long as the temperature is above 37°F (about 3°C). Central Kentucky has experienced a particularly warm winter thus far.

Townsend said cold temperatures will slow their development, but the tent and general cold hardiness of the species will keep them from being affected drastically even if temperatures drop below freezing at night.

Unless horse farm managers have been aggressive in managing Eastern tent caterpillars or removing host trees, UK entomologists recommend they keep pregnant mares out of pastures bordered by cherry trees for the next several weeks.

“Foliar sprays for caterpillar control can be made when tents are about the size of a baseball,” Townsend said. “Another option is the injection of trees with a systemic insecticide by commercial pesticide applicators or arborists. Regardless of the treatment used, it is important to revisit the sites in about five days to assess caterpillar activity."

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